1. Field
The present disclosure relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a three-dimensional semiconductor device.
2. Description of the Related Art
A three-dimensional (3D) semiconductor device, in which memory cells are formed in a 3D structure for high integration of the semiconductor device, has been suggested. A 3D semiconductor device is capable of efficiently utilizing an area of a substrate when compared to a two-dimensional (2D) semiconductor device, therefore, the 3D semiconductor device may easily improve a degree of integration.
Recently, due to a high demand for portable electronic devices, research on high-integration and large capacity semiconductor devices have been actively conducted. Among the semiconductor devices which are widely used, is a flash memory device, in which stored data is maintained even though a supply of power is cut off.
The flash memory device may include a memory cell array, in which data is stored, a peripheral circuit which performs program, read, and erase operations of the memory cell array, and a control circuit controlling the peripheral circuit. The memory cell array may include a plurality of memory blocks. Each of the memory blocks may include a plurality of vertical strings.
In the 3D semiconductor device, the vertical strings may be vertically formed on a semiconductor substrate. For example, the vertical strings may include a plurality of select transistors and memory cells vertically stacked on the substrate.
The vertical strings may be formed in a Bit-Cost Scalable (BICS) or Pipe-shape Bit-Cost Scalable (P-BICS) structure according to a form thereof. The vertical strings in the BICS structure may be formed in a shape of “I”, and the vertical strings in the P-BICS structure may be formed in a shape of “U”. Since the vertical strings in the BICS structure are formed in a shape of “I”, each of the vertical strings forms a unit structure. On the other hand, since the vertical strings in the P-BICS structure are formed in a shape of “U”, a pair of vertical strings are connected with each other through a pipe channel to form a unit structure.